SHANGHAI, Aug. 8 (Xinhua) -- The Shanghai World Expo marked its 100th day Sunday, with the first group of visitors arriving as early as 4 a.m.

Some, like Ni Dan from eastern Jiangsu Province, even chose to stay overnight in front of the Expo Park entrance to guarantee obtaining tickets to some of the most popular pavilions.

Ni, 20, and two of his classmates were the first visitors entering the Expo Park Sunday.

Ni said, "We chose to visit Expo today for three reasons: it's the Expo's 100th day; it's the second anniversary of the Beijing Olympic Games; plus it's the eighth day of the eighth month, which is considered by many an auspicious number."

Sitting on the ground or on 10-yuan (about 1.5 U.S. dollars) plastic folding stools newly purchased from vendors, people chatted, played cards or meditated to reserve energy for a very long day of waiting, walking, viewing and waiting again.

Nearly 38 million visitors, about 95 percent of whom are Chinese and nearly 80 percent are non-Shanghainese, have come to the Expo Park since its opening on May 1, and an average of about 450,000 visitors came to the Expo Park per day in August, equal to the population of a mid-level Chinese county, according to the Expo bureau.

The bureau also said shuttle buses in the Expo park have carried nearly 100 million visitors since the Park's opening, as the buses were out on a run every 14 seconds.

The sudden influx of people has challenged the city's level of openness and hospitality, similar to what Beijing faced during the Olympics two years ago.

Hu Xinyu, a 22-year-old local resident who was back home this year from studying overseas, said Shanghai was greatly changed by the mega event. Hu was surprised to find that many taxi drivers could speak English and volunteers both in and outside the Expo Park were always ready to help.

During the 184 days of the Expo, the number of volunteers will reach about 680,000, including those from 24 foreign countries. This greatly exceeds the 76,000 volunteers assisting during the Beijing Olympics. Most Expo volunteers are from the post-1980 and post-1990 generations.

Xu Yuan of Shanghai Normal University is a volunteer who has worked in both the Shanghai Expo and the Beijing Olympic Games in 2008.

Being an experienced volunteer, Xu still found the most difficult part of volunteering is answering questions. Xu was often besieged by a dozen Expo visitors asking a variety of questions.

-- "The French and Spanish Pavilion, which one I should go to?"

-- "How do I get to the Bund?"

-- "How far is it between Monaco and Morocco?"

-- "Is it Indonesia or India?"

Xu said quick responses were always needed in answering these questions.

Meanwhile, services provide to visitors have been carefully designed. The staff of the German Pavilion delivered "toilet coupons" to visitors in the long queue, which settled the problem of going to the washroom while queuing, as visitors could return to their original place in the queue after visiting a washroom.

Staff at the pavilion of the Republic of Korea (ROK) handed out bottled water to visitors waiting in the queue. The ROK pavilion is so popular that more than three hours of queuing is needed for a visit.

Volunteers also scattered at Expo Park entrances to hand out fans and maps. Additionally, huge ice cubes were put in buckets beside queues to cool visitors waiting to enter pavilions.

Tu Qiyu, a research fellow with the Shanghai Academy of Social Sciences, said the Expo is a joint effort by both China and the world, as many nations valued this opportunity to present themselves, such as Denmark that is displaying its "Little Mermaid" and Saudi Arabia, which spent an enormous amount of money to build its pavilion. "Even Iceland, which was struck hard by the financial crisis, has made elaborate preparations for the exhibition."

"The world has been condensed into 5.28 sq km," Tu said.

Also on Sunday, Cote d'Ivoire celebrated its National Pavilion day with African aboriginal dances and lively drumbeats. Since May 1, more than 80 National Pavilion Days have been marked to show the charm of these countries, with officials or even top leaders of these countries participating in the events, followed by business delegations. Enditem